Method for performing timing measurement for location estimation of an electronic device with aid of one request sent to multiple peer devices, and associated apparatus

ABSTRACT

A method and apparatus for performing timing measurement for location estimation of an electronic device are provided, where the method includes the steps of: sending a pre-association broadcast request frame to trigger multiple responders in a wireless network system to initiate timing measurement; and performing timing measurement according to a plurality of timestamps, for determining a location of the electronic device, wherein for a specific responder of the responders, a first timestamp and a second timestamp within the plurality of timestamps respectively correspond to a time of departure (ToD) and a time of arrival (ToA) of a pre-association uni-cast response frame received from the specific responder, and a third timestamp and a fourth timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement frame corresponding to the pre-association uni-cast response frame, the acknowledgement frame sent from the electronic device to the specific responder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/813,198, which was filed on Apr. 18, 2013, and is included herein by reference.

BACKGROUND

The present invention relates to location estimation with a reduced number of frame exchanges between electronic devices in a wireless network system, and more particularly, to a method for performing timing measurement for location estimation of an electronic device, and to an associated apparatus.

According to the related art, a conventional electronic device in a wireless network system can be designed to determine the location of the conventional electronic device in a situation where the locations of three points in the wireless network system and the time of flight (or the time of electromagnetic wave propagation) between the conventional electronic device and each of the three points are known. However, some problems may occur. For example, multiple requests are required for triggering the timing measurement corresponding to the aforementioned three points, respectively. In another example, before performing the timing measurement respectively corresponding to the aforementioned three points, it is typically required to send additional probe frames from the conventional electronic device to discover peer devices in the wireless network system, causing the power consumption of the conventional electronic device to be increased. More particularly, as the number of frame exchanges for the timing measurement is typically proportional to the number of peer devices under consideration and the frequency of updates, the total channel capacity of the wireless network system may be insufficient in some situations (e.g. the frequency of updates increases, and/or the number of users who need positioning in the wireless network system is many). Thus, a novel method is required for improving the location estimation of an electronic device in a wireless network system.

SUMMARY

It is an objective of the claimed invention to provide a method for performing timing measurement for location estimation of an electronic device, and to an associated apparatus, in order to solve the above-mentioned problems.

It is another objective of the claimed invention to provide a method for performing timing measurement for location estimation of an electronic device, and to an associated apparatus, in order to reduce the number of frame exchanges in a wireless network system.

According to at least one preferred embodiment, a method for performing timing measurement for location estimation of an electronic device is provided, where the method comprises the steps of: sending a pre-association broadcast request frame to trigger multiple responders in a wireless network system to initiate timing measurement; and performing timing measurement according to a plurality of timestamps, for determining a location of the electronic device, wherein a portion of the plurality of timestamps is obtained from the responders. For example, at least one timestamp is determined based on a pre-association uni-cast response frame received from one of the responders, wherein no actual association is established between the electronic device and any of the responders. More particularly, for a specific responder of the responders (e.g. the aforementioned one of the responders), a first timestamp and a second timestamp within the plurality of timestamps respectively correspond to a time of departure (ToD) and a time of arrival (ToA) of a pre-association uni-cast response frame received from the specific responder, and a third timestamp and a fourth timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement frame corresponding to the pre-association uni-cast response frame received from the specific responder, the acknowledgement frame sent from the electronic device to the specific responder. For example, the pre-association broadcast request frame can be a probe request frame, and the pre-association uni-cast response frame received from the specific responder can be a probe response frame. In another example, the pre-association broadcast request frame can be a Generic Advertisement Service (GAS) request frame, and the pre-association uni-cast response frame received from the specific responder can be a GAS response frame.

According to at least one preferred embodiment, an apparatus for performing timing measurement for location estimation of an electronic device is provided, where the apparatus comprises at least one portion of the electronic device. The apparatus comprises a processing circuit arrange to control operations of the electronic device, and further comprises a transceiver arranged to transmit or receive information for the electronic device, where the processing circuit is coupled to the transceiver. In addition, the processing circuit sends, by utilizing the transceiver, a pre-association broadcast request frame to trigger multiple responders in a wireless network system to initiate timing measurement, and performs timing measurement according to a plurality of timestamps, for determining a location of the electronic device, wherein a portion of the plurality of timestamps is obtained from the responders. For example, at least one timestamp is determined based on a pre-association uni-cast response frame received from one of the responders, wherein no actual association is established between the electronic device and any of the responders. More particularly, for a specific responder of the responders (e.g. the aforementioned one of the responders), a first timestamp and a second timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of a pre-association uni-cast response frame received from the specific responder, and a third timestamp and a fourth timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement frame corresponding to the pre-association uni-cast response frame received from the specific responder, the acknowledgement frame sent from the electronic device to the specific responder. For example, the pre-association broadcast request frame can be a probe request frame, and the pre-association uni-cast response frame received from the specific responder can be a probe response frame. In another example, the pre-association broadcast request frame can be a GAS request frame, and the pre-association uni-cast response frame received from the specific responder can be a GAS response frame.

It is an advantage of the present invention that the present invention method and apparatus can use merely one request (more particularly, a request sent from the electric device to multiple peer devices) to immediately start performing timing measurement for location estimation. In addition, in comparison with the related art, the number of frame exchanges in a wireless network system is greatly reduced, where additional probe frames are not required. As a result, the power consumption can be decreased, and the problem of insufficiency of the total channel capacity of the wireless network system can be prevented.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an apparatus for performing timing measurement for location estimation of an electronic device according to a first embodiment of the present invention.

FIG. 2 illustrates a wireless network system comprising the aforementioned electronic device according to an embodiment of the present invention.

FIG. 3 illustrates a flowchart of a method for performing timing measurement for location estimation of an electronic device according to an embodiment of the present invention.

FIG. 4 illustrates a control scheme involved with the method shown in FIG. 3 according to an embodiment of the present invention.

DETAILED DESCRIPTION

Certain terms are used throughout the following description and claims, which refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

Please refer to FIG. 1, which illustrates a diagram of an apparatus 100 for performing timing measurement for location estimation of an electronic device according to a first embodiment of the present invention, where the apparatus 100 may comprise at least one portion (e.g. a portion or all) of the electronic device. For example, the apparatus 100 may comprise a portion of the electronic device mentioned above, and more particularly, can be at least one hardware circuit such as at least one integrated circuit (IC) within the electronic device. In another example, the apparatus 100 can be the whole of the electronic device mentioned above. In another example, the apparatus 100 may comprise a system comprising the electronic device mentioned above (e.g. an audio/video system comprising the electronic device). Examples of the electronic device may include, but not limited to, a mobile phone (e.g. a multifunctional mobile phone), a personal digital assistant (PDA), and a personal computer such as a laptop computer.

As shown in FIG. 1, the apparatus 100 may comprise a processing circuit 110 arrange to control operations of the electronic device, and may further comprise a transceiver 120 arranged to transmit or receive information for the electronic device, where the transceiver 120 is coupled to the processing circuit 110, and one or more antennas of the electronic device may be coupled to the transceiver 120. For example, the processing circuit 110 may comprise at least one processor and associated hardware resources, and the transceiver 120 may comprise a transmitter and a receiver such as those for wireless network communications, where the processor may execute some program codes 110P retrieves from a storage module (e.g. a hard disk drive (HDD), or a non-volatile memory such as a Flash memory) within the electronic device to control the aforementioned operations of the electronic device.

According to this embodiment, the processing circuit 110 may send, by utilizing the transceiver 120, a pre-association broadcast request frame to trigger some peer devices in a wireless network system to initiate timing measurement. The peer devices may respond to the pre-association broadcast request frame by sending pre-association uni-cast response frames to the electronic device, respectively, so the aforementioned timing measurement can be performed immediately. Thus, the electronic device can be regarded as the initiator, and the peer devices can be regarded as the responders. More particularly, the initiator may uses the pre-association broadcast (or multicast) request frame, such as a probe request or a Generic Advertisement Service (GAS) request, as a timing measurement request to solicit multiple responders to directly perform timing measurement operations such as some interactions for measuring the time of flight (or the time of electromagnetic wave propagation) between the electronic device and each of the responders whose locations are known. For example, each of the responders may send a pre-association uni-cast response frame, such as a probe response frame or a GAS response frame, as a timing measurement frame. Regarding determining the location of the electronic device in a situation where the locations of three points in the wireless network system and the time of flight (or the time of electromagnetic wave propagation) between the electronic device and each of the three points are known, please refer to Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (e.g. “IEEE 802.11-2012” standards) for more information when needed.

As a result of using the pre-association broadcast request frame to simultaneously trigger the responders to initiate the timing measurement, the total number of exchange frames of multiple peers can be reduced significantly in comparison with the related art, where it is unnecessary to perform peer-to-peer IEEE 802.11v timing measurement frame handshaking of the related art before the feedback of the timing measurement report. In addition, the time and power consumption of the additional discovery phase of the related art and the information query phase of the related art can be saved since all information required can be obtained during (or before) the timing measurement process triggered by the pre-association broadcast request frame. For example, the locations of the three points can be carried by the aforementioned pre-association uni-cast response frames, and therefore can be sent to the electronic device right after the pre-association broadcast request frame is sent. In another example, the locations of the three points can be retrieved from the Internet or somewhere else in the wireless network system in advance, rather than being sent from the responders at this moment during the timing measurement.

FIG. 2 illustrates a wireless network system 200 comprising the aforementioned electronic device of the embodiment shown in FIG. 1 according to an embodiment of the present invention, where the wireless network system 200 can be taken as an example of the aforementioned wireless network system in the embodiment shown in FIG. 1. As shown in FIG. 2, the electronic device in this embodiment (labeled “STA” in FIG. 2, where the notation “STA” stands for “Station”) may move from a point to another point since the user of the electronic device may carry the electronic device to walk around. For example, the user carrying the electronic device may walk to the center of the region 205-1, and the apparatus 100 may control the electronic device to send a single request (labeled “Request” in FIG. 2) to start performing timing measurement for location estimation corresponding to the center of the region 205-1, and then some of the peer devices (labeled “AP” in FIG. 2, where the notation “AP” stands for “Access Point”) in the wireless network system 200 is triggered to send responses to the electronic device, respectively, where the notations “1” and “2” labeled on the request and the responses illustrated within the region 205-1 indicate that the request is sent first and then the responses are sent. Similarly, the user carrying the electronic device may walk to the center of the region 205-2, and the apparatus 100 may control the electronic device to send a single request to start performing timing measurement for location estimation corresponding to the center of the region 205-2, in order to update the location of the electronic device. Similarly, the user carrying the electronic device may walk to the center of the region 205-3, and the apparatus 100 may control the electronic device to send a single request to start performing timing measurement for location estimation corresponding to the center of the region 205-3, in order to update the location of the electronic device.

FIG. 3 illustrates a flowchart of a method 300 for performing timing measurement for location estimation of an electronic device according to an embodiment of the present invention. The method shown in FIG. 3 can be applied to the apparatus 100 shown in FIG. 1 (more particularly, the electronic device STA of the embodiment shown in FIG. 2), and can be applied to the processing circuit 110 thereof (more particularly, the processing circuit 110 executing the program codes 110P of the embodiment shown in FIG. 1). The method is described as follows.

In Step 310, the processing circuit 110 sends, by utilizing the transceiver 120, a pre-association broadcast request frame such as that mentioned above to trigger multiple responders in a wireless network system such as the wireless network system 200 to initiate the timing measurement. For example, the pre-association broadcast request frame can be a probe request frame. In another example, the pre-association broadcast request frame can be a GAS request frame.

In Step 320, the processing circuit 110 performs timing measurement according to a plurality of timestamps, for determining a location of the electronic device, where a portion of the plurality of timestamps can be obtained from the responders, and another portion of the plurality of timestamps can be determined within the electronic device. For example, within the plurality of timestamps, at least one timestamp can be determined based on a pre-association uni-cast response frame received from one of the responders, such as the pre-association uni-cast response frame mentioned in the embodiment shown in FIG. 1. More particularly, no actual association is established between the electronic device and any of the responders.

According to this embodiment, for a specific responder of the responders (e.g. the aforementioned one of the responders), a first timestamp t1 and a second timestamp t2 within the plurality of timestamps respectively correspond to a time of departure (ToD) and a time of arrival (ToA) of a pre-association uni-cast response frame received from the specific responder, and a third timestamp t3 and a fourth timestamp t4 within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement (or ACK) frame corresponding to this pre-association uni-cast response frame, the acknowledgement frame sent from the electronic device to the specific responder. For example, in a situation where the pre-association broadcast request frame is a probe request frame, this pre-association uni-cast response frame can be a probe response frame. In another example, in a situation where the pre-association broadcast request frame is a GAS request frame, this pre-association uni-cast response frame can be a GAS response frame.

More particularly, the aforementioned specific responder may represent each responder of at least one portion (e.g. a portion or all) of the responders. For example, the specific responder may represent each responder of a portion of the responders. This is for illustrative purposes only, and is not meant to be a limitation of the present invention. In another example, the specific responder may represent each of the responders.

According to some embodiments of the present invention, such as some variations of the embodiment shown in FIG. 3, as updating the location of the electronic device may be needed, the whole working flow of the method 300 can be repeated. For example, after the operations of Step 320 are completed, Step 310 can be re-entered for updating the location of the electronic device.

FIG. 4 illustrates a control scheme involved with the method 300 shown in FIG. 3 according to an embodiment of the present invention, where the electronic device (labeled “The initiator” in FIG. 4, for better comprehension) may perform operations under control of the processing circuit 110. For a specific responder such as that mentioned above, the meanings of the timestamps {t1, t2, t3, t4} can be the same as that of the embodiment shown in FIG. 3, where another set of timestamps {t1′, t2′, t3′, t4′} may represent the associated timestamps corresponding another responder within the responders mentioned in Step 310 (more particularly, any of the other responders within the responders mentioned in Step 310, i.e. any responder within the responders mentioned in Step 310 except for the specific responder mentioned above).

As shown in FIG. 4, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), uses a single request frame such as the aforementioned pre-association broadcast request frame (e.g. a probe request, or a GAS request) to trigger multiple responders to initiate the timing measurement, where the time-measurement-related operations of the responders are triggered by the same request frame, and more particularly, can be triggered at the same time. For example, the specific responder may send one of the uni-cast response frames shown in FIG. 4, such as the pre-association uni-cast response frame sent at the time represented by the timestamp t1, to the initiator. Then, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), may send the corresponding acknowledgement frame (labeled “ACK” in FIG. 4, for brevity) to the specific responder. As the timestamps t1 and t4 can be obtained (or captured) by the specific responder while the timestamps t2 and t3 can be obtained (or captured) by the initiator, the specific responder may send a timing measurement report (labeled “TM report” in FIG. 4, for brevity) such as a uni-cast report frame carrying the timestamps t1 and t4 to the initiator, where the initiator may send another acknowledgement frame (labeled “ACK” in FIG. 4, for brevity) to acknowledge the reception of this timing measurement report. Thus, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), can determine or estimate the time of flight (ToF) relative to the specific responder sending this timing measurement report based on the following equation:

ToF=((t4−t1)−(t3−t2))/2;

where the distance between the initiator and the specific responder can be determined or estimated to be (c*ToF), with the notation “c” representing the speed of light in vacuum. That is, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), can determine or estimate the distance between the initiator and the specific responder based on the following equation:

D=(c*ToF)=c*((t4−t1)−(t3−t2))/2;

where the notation “D” represents the distance between the initiator and the specific responder. As a result, the distance D between the electronic device and the specific responder can be utilized for determining the location of the electronic device.

Please note that similar operations may be applied to the interactions between the initiator and another responder such as that mentioned above (more particularly, any of the other responders within the responders mentioned in Step 310, i.e. any responder within the responders mentioned in Step 310 except for the specific responder mentioned above). In another example, the other responder may send another one of the uni-cast response frames shown in FIG. 4, such as the pre-association uni-cast response frame sent at the time represented by the timestamp t1′, to the initiator. Then, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), may send the corresponding acknowledgement frame (labeled “ACK” in FIG. 4, for brevity) to the other responder. As the timestamps t1′ and t4′ can be obtained (or captured) by the other responder while the timestamps t2′ and t3′ can be obtained (or captured) by the initiator, the other responder may send a timing measurement report (labeled “TM report” in FIG. 4, for brevity) such as a uni-cast report frame carrying the timestamps t1′ and t4′ to the initiator, where the initiator may send another acknowledgement frame (labeled “ACK” in FIG. 4, for brevity) to acknowledge the reception of this timing measurement report. Thus, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), can determine or estimate the time of flight (denoted ToF′ for this example to prevent confusion) relative to the other responder sending this timing measurement report based on the following equation:

ToF′=((t4′−t1′)−(t3′−t2′))/2;

where the distance between the initiator and the other responder can be determined or estimated to be (c*ToF′), with the notation “c” representing the speed of light in vacuum. That is, the initiator, i.e. the electronic device of this embodiment (more particularly, the processing circuit 110 therein), can determine or estimate the distance between the initiator and the other responder based on the following equation:

D′=(c*ToF′)=c*((t4′−t1′)−(t3′−t2′))/2;

where the notation “D′” represents the distance between the initiator and the other responder. As a result, the distance D′ between the electronic device and the other responder can be utilized for determining the location of the electronic device.

In general, the equations disclosed above can be collectively expressed as follows:

ToF(n)=((t4(n)−t1(n))−(t3(n)−t2(n)))/2; and

D(n)=(c*ToF(n))=c*((t4(n)−t1(n))−(t3(n)−t2(n)))/2;

where the index n corresponds to the responder under consideration within the responders, such as the responder R(n) (e.g. the specific responder, or the other responder mentioned above). Thus, the initiator and the responder R(n) are arranged to capture four timestamps including ToDs and ToAs for a transmitted response frame and the corresponding ACK frame, respectively, where the responder R(n) uses a uni-cast report frame to provide its locally captured timestamps to the initiator. As a result, the initiator can determine or estimate a set of time of flight {ToF(n)} relative to the aforementioned multiple responders using the plurality of timestamps. In addition, the initiator can further determine or estimate a set of distances {D(n)} between the initiator and the responders {R(n)}, respectively, in order to determine the location of the initiator, i.e. the location mentioned in Step 320. Please note that the initiator may utilize a terminate frame (which is a broadcast or multicast frame) to cancel the measurement process if known points are enough to calculate the aforementioned location of the electronic device.

Based on the method 300 shown in FIG. 3, and more particularly, the control scheme shown in FIG. 4, the processing circuit 110 can perform the aforementioned timing measurement according to the plurality of timestamps, without need to establish the association between the initiator (i.e. the electronic device) and any of the responders {R(n)} first. For example, the processing circuit 110 can perform the aforementioned timing measurement according to the plurality of timestamps, without establishing the association between the initiator (i.e. the electronic device) and any of the responders {R(n)} in advance. In comparison with the related art, the number of frame exchanges in the wireless network system can be greatly reduced based on the embodiments disclosed above.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A method for performing timing measurement for location estimation of an electronic device, the method being applied to the electronic device, the method comprising the steps of: sending a pre-association broadcast request frame to trigger multiple responders in a wireless network system to initiate timing measurement; and performing timing measurement according to a plurality of timestamps, for determining a location of the electronic device, wherein a portion of the plurality of timestamps is obtained from the responders, wherein at least one timestamp is determined based on a pre-association uni-cast response frame received from one of the responders; wherein no actual association is established between the electronic device and any of the responders.
 2. The method of claim 1, wherein a portion of the plurality of timestamps is determined within the electronic device.
 3. The method of claim 1, wherein for a specific responder of the responders, a first timestamp and a second timestamp within the plurality of timestamps respectively correspond to a time of departure (ToD) and a time of arrival (ToA) of a pre-association uni-cast response frame received from the specific responder, and a third timestamp and a fourth timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement frame corresponding to the pre-association uni-cast response frame received from the specific responder, the acknowledgement frame sent from the electronic device to the specific responder.
 4. The method of claim 3, wherein the step of performing timing measurement according to the plurality of timestamps for determining the location of the electronic device further comprises: determining a time of flight (ToF) relative to the specific responder based on the equation of: ToF=((t4−t1)−(t3−t2))/2; wherein the notations “t1”, “t2”, “t3”, and “t4” represent the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp, respectively.
 5. The method of claim 4, wherein the step of performing timing measurement according to the plurality of timestamps for determining the location of the electronic device further comprises: determining a distance between the electronic device and the specific responder based on the equation of: D=(c*ToF); wherein the notation “D” represents the distance between the electronic device and the specific responder, and the notation “c” represents the speed of light in vacuum; and the distance between the electronic device and the specific responder is utilized for determining the location of the electronic device.
 6. The method of claim 1, wherein the pre-association broadcast request frame is a probe request frame, and the pre-association uni-cast response frame is a probe response frame.
 7. The method of claim 1, wherein the pre-association broadcast request frame is a Generic Advertisement Service (GAS) request frame, and the pre-association uni-cast response frame is a GAS response frame.
 8. An apparatus for performing timing measurement for location estimation of an electronic device, the apparatus comprises at least one portion of the electronic device, the apparatus comprising: a transceiver arranged to transmit or receive information for the electronic device; and a processing circuit, coupled to the transceiver, arranged to control operations of the electronic device, wherein the processing circuit sends, by utilizing the transceiver, a pre-association broadcast request frame to trigger multiple responders in a wireless network system to initiate timing measurement, and performs timing measurement according to a plurality of timestamps, for determining a location of the electronic device, wherein a portion of the plurality of timestamps is obtained from the responders, wherein at least one timestamp is determined based on a pre-association uni-cast response frame received from one of the responders; wherein no actual association is established between the electronic device and any of the responders.
 9. The apparatus of claim 8, wherein a portion of the plurality of timestamps is determined within the electronic device.
 10. The apparatus of claim 8, wherein for a specific responder of the responders, a first timestamp and a second timestamp within the plurality of timestamps respectively correspond to a time of departure (ToD) and a time of arrival (ToA) of a pre-association uni-cast response frame received from the specific responder, and a third timestamp and a fourth timestamp within the plurality of timestamps respectively correspond to a ToD and a ToA of an acknowledgement frame corresponding to the pre-association uni-cast response frame received from the specific responder, the acknowledgement frame sent from the electronic device to the specific responder.
 11. The apparatus of claim 10, wherein the processing circuit determines a time of flight (ToF) relative to the specific responder based on the equation of: ToF=((t4−t1)−(t3−t2))/2; wherein the notations “t1”, “t2”, “t3”, and “t4” represent the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp, respectively.
 12. The apparatus of claim 11, wherein the processing circuit determines a distance between the electronic device and the specific responder based on the equation of: D=(c*ToF); wherein the notation “D” represents the distance between the electronic device and the specific responder, and the notation “c” represents the speed of light in vacuum; and the distance between the electronic device and the specific responder is utilized for determining the location of the electronic device.
 13. The apparatus of claim 8, wherein the pre-association broadcast request frame is a probe request frame, and the pre-association uni-cast response frame is a probe response frame.
 14. The apparatus of claim 8, wherein the pre-association broadcast request frame is a Generic Advertisement Service (GAS) request frame, and the pre-association uni-cast response frame is a GAS response frame. 